-LRB- CNN -RRB- -- Federal support for renewable power helped the United States reclaim from China the title of the world 's biggest investor in clean energy , researchers for the nonprofit Pew Charitable Trusts reported Wednesday .

The $ 48 billion in U.S. private investment in technology such as wind turbines and solar panels in 2011 edged out China 's $ 45.5 billion , Pew researchers found in a new study . Worldwide , investors put $ 263 billion into renewable energy projects last year -- a 6.5 % increase over 2010 -- and the cost of producing electricity from solar power was cut in half , the study found .

But the U.S. gains have been boosted by government incentives , including provisions of the 2009 economic stimulus package , that are due to disappear within two years , said Phyllis Cuttino , director of Pew 's clean energy programs .

`` Those countries that have long-term policies in place are the ones that have had consistent growth , '' Cuttino told CNN . `` And we do n't have that . ''

And while U.S. investors have been ponying up while the incentives are in place , much of that money is going into projects overseas -- and America is importing the resulting products .

`` The United States is , frankly , missing an opportunity if we do not manufacture and export to these counties with growing middle classes who are going to be purchasing these products , '' Cuttino said .

Solar , wind , biomass and small-scale hydroelectric projects installed worldwide had the capability to produce about 565 billion watts , or 565 gigawatts , of electricity in 2011 , the report found . That 's about 10 percent of the worldwide total , and roughly enough to reduce carbon emissions most scientists blame for a warming climate by between 3 % to 6 % , according to analysts at the Breakthrough Institute , a California-based think tank that concentrates on energy and the environment .

In the United States , renewables other than hydroelectric provide about 4.7 % of U.S. generating capacity , according to figures from the U.S. Energy Information Administration .

Germany saw the third-largest investment in alternative energy with nearly $ 31 billion in 2011 , even though that figure was down 5 % from 2010 , the Pew report found . The Germans added more than 7 gigawatts of solar energy capacity in 2011 , while Italian investments grew by nearly 40 % to $ 28 billion . Italy added about 8 gigawatts of solar energy , mostly in small-scale projects .

And India saw a 54 percent increase in support for clean energy . Indian projects grew to $ 10.2 billion , adding 2.8 gigawatts in wind power .

Germany and China have boosted their green energy sector `` through consistent policies , '' by setting targets for new generating capacity , the report said .

`` What that tells investors is , ` Go there -- they 're in it for the long term , ' '' Cuttino said . `` They 're not going to let that expire in 2013 . '' Meanwhile , no new U.S. wind projects have been commissioned for 2014 , she said .

The United States is also seeing a boom in cheap natural gas , which produces fewer carbon emissions than coal or oil . And in the past year , the collapse of the solar energy firm Solyndra has cast a pall over alternative energy funding in the United States .

Solyndra filed for bankruptcy in 2011 after receiving more than $ 535 million in federal loan guarantees , putting more than 1,000 people out of work . President Barack Obama 's Republican opposition has attacked the loan-guarantee program as `` crony capitalism , '' accusing Solyndra of receiving special treatment because a key investor was an Obama fundraiser , but supporters say the company was undermined by the explosive growth of China 's solar industry .

Cuttino said companies are going to fail as the renewable power industry grows , comparing it to the early years of the automobile industry .

`` There were over 100 companies trying to make cars at the turn of the century , '' she said . `` And now we basically have three . ''

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Government incentives boost U.S. investment in green power , Pew says

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But many of those incentives will expire in the next two years

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Countries that have long-term policies draw more investment